• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.128-136
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• 2011

An approach to improve the performance of SDINS and GPS integrated system for bank-to-turn flight vehicles is described. Then, it is shown through the simulation that a specific gyro misalignment error results in an increased heading error of SDINS. A new modelling method is presented herein for identifying of sensor and attitude error. The main advantage of the proposed method is that it not only estimates the gyro misalignment error of SDINS, but also improves estimate performance of heading error of SDINS in the presence of the gyro misalignments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.574-581
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• 2019

This paper investigates the effects of thrust misalignments and offsets of the lateral center of gravity of a space launch vehicle on its guidance performance. Sensitivity analysis and Monte Carlo simulations are applied to analyze their effects by computing changes in orbit injection errors when including the error sources. To compensate their effects, the attitude controller including an integrator additionally and the Steering Misalignment Correction (SMC) routine of the Saturn V are considered, and then Monte Carlo simulations are performed to evaluate their performances.

• Journal of Advanced Navigation Technology
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• v.26 no.3
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• pp.160-165
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• 2022

In this paper, we have proposed a magnetic resonant 6.78MHz WPT(wireless power transfer) technique which can be applied to a fixed transmitter and a receiver of varying relative distance and coil alignment, Power transmission characteristics are studied with the relative distance and misalignment ration of coil area between the transmitting and receiving coils. The coils are designed with the size of 60×80mm² by direct feeding method, and the characteristics are derived with the maximum relative distance of 50mm and horizontal area misalignment state of 0-40mm misalignment of coil center axis in the XY plane. The power transmission characteristics are compared between the 3D EM simulation and the measured data, and the power transmission shows larger than -3dB performance with the vertical distance of up to 30mm and 50% area misalignmment ratio. This work showsthe transmission characteristics according to relative distance and misalignment state between the cols and that direct feeding has advantage for the short relative distance and small misalignment ratio.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.4
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• pp.181-186
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• 2015

A High-degree Cubature Kalman Filter (CKF) is proposed to deal with the Strapdown Inertial Navigation System (SDINS) alignment problem. In-flight Alignment (IFA) is an effective method to compensate for attitude errors of the navigation system. While providing precise attitude error compensation, however, the external source aided alignment often creates a nonlinear filtering problem caused by a large misalignment angle. Introduced recently, Cubature Kalman Filter is a suitable technique for various nonlinear problems. In this paper, a higher degree CKF is applied to this accuracy-is-everything SDINS IFA problem. The simulation results show that the proposed technique outperformed a traditional nonlinear filter in terms of precision and alignment time.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.433-439
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• 2018

In this paper, a SDINS(strapdown inertial navigation system) rapid initial alignment technique with adaptive time delay compensation is proposed. The proposed method consists of two steps. In first step, misalignment and data latency are estimated by conducting pre-transfer alignment. Then, hybrid alignment is designed to rapidly find the misalignment changes induced by pyro-shock. To improve the performance of hybrid alignment, adaptive time delay compensation method is suggested. We verify the performance improvement of the proposed alignment scheme comparing with the conventional transfer alignment method by van test. The test result shows that the proposed alignment technique improves alignment performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.32-39
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• 2004

This research is to investigate the performance of a flexible matrix composite driveshaft with respect to shaft design parameters such as the number of layers, ply orientations, and material properties. A finite element formulation is utilized to estimate the allowable misalignment under given driving torque, the maximum temperature at steady states, and external damping for ensuring whirling stability under supercritical speed. Results indicate that the system performance can be greatly affected by the shaft laminate parameters, especially the ply orientations. Several sets of shaft parameters that will provide satisfactory overall system performance are derived.

• Journal of Astronomy and Space Sciences
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• v.23 no.4
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• pp.327-336
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• 2006

In this paper, gain loss of KVN (Korean VLBI Network) 21-m shaped Cassegrain antenna due to misalignment of antenna optics is calculated using ray-tracing method. It enables us to estimate alignment tolerances of feed and sub-reflector positioning. According to numerical results, KVN 21-m shaped Cassegrain antenna's gain loss is more sensitive to positions of feed and sub-reflector than in case of the equivalent classical Cassegrain antenna. The result of calculation is believed to be utilized as a possible guideline when checking the performance of the antenna system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.213-216
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• 2001

A micro hole punching system was developed and micro holes of 100m in diameter were successfully made on brass sheets of loom in thickness. A micro punch made of tungsten carbide was designed to withstand the punch load, considering the buckling and the bending moment due to possible misalignment error. The punch was fabricated by the grinding process with diamond wheel. The die was designed considering the punch load and fabricated by micro electrodischarge machining process. In this system the stripper is designed to guide punch tip to minimize the possible misalignment. The punch was installed on a vertical stepper and the die was mounted on an X-Y translation unit. The precision motion controller controlled all motions of the micro hole punching system. In this study technical difficulties and solutions in the micro hole punching process were also discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.867-870
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• 1996

Often an INS has to be aligned in navigation. In these cases it is necessary to obtain some reference information on the state of the aligned INS(Slave) such as its position, its velocity of its angular rate. Usually the reference information is velocity which is supplied by another reference INS. In the alignment state the velocity computed by the reference INS(Master) is compared with that computed by the slave INS and the difference which is indicative of the slave misalignment with respect to the master, is processed by a Kalman filter which estimates misalignment as well as the slave gyro and accelerometer error states. The operation of aligning a slave INS with a master INS comparing quantities computed by both INS is known as transfer alignment. The delivery vehicle performs error these maneuvers enable the TA Kalman filter to separate between the tilt errors and the accelerometer biases which otherwise are unobservable. The basic objective this paper is to study the observability enhancement by ship's maneuvering and matching methods during transfer alignment at sea.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.241-245
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• 2005

Strapdown inertial navigation system (SINS) integrated with astronavigation system (ANS) yields reliable mission capability and enhanced navigational accuracy for spacecrafts. The theory and characteristics of integrated system based on unscented Kalman filtering is investigated in this paper. This Kalman filter structure uses unscented transform to approximate the result of applying a specified nonlinear transformation to a given mean and covariance estimate. The filter implementation subsumed here is in a direct feedback mode. Axes misalignment angles of the SINS are observation to the filter. A simple approach for simulation of axes misalignment using stars observation is presented. The SINS error model required for the filtering algorithm is derived in space-stabilized mechanization. Simulation results of the integrated navigation system using a medium accuracy SINS demonstrates the validity of this method on improving the navigation system accuracy with the estimation and compensation for gyros drift, and the position and velocity errors that occur due to the axes misalignments.